Dopamine inhibits AVP-dependent Na+ transport and water permeability in rat CCD via a D4-like receptor

1996 ◽  
Vol 271 (2) ◽  
pp. F391-F400 ◽  
Author(s):  
D. Sun ◽  
J. A. Schafer
Keyword(s):  
Water Transport ◽  
Water Permeability ◽  
Sch 23390 ◽  
Na Transport ◽  
D2 Agonist ◽  
Osmotic Water ◽  
D1 Agonists ◽  
Transepithelial Voltage ◽  
Specific Antagonist ◽  
Type Receptor

We studied the receptor responsible for dopamine action in isolated perfused cortical collecting ducts (CCD) from rats treated with deoxy-corticosterone. (Critical experiments were repeated in CCD from untreated rats with the same results.) At doses > or = 1 microM, dopamine inhibited arginine vasopressin (AVP)-dependent Na+ and water transport (measured by the unidirectional lumen-to-bath 22Na+ flux and the transepithelial voltage) and osmotic water permeability (Pf). The effects of dopamine were not reversed by the dopamine-1 (D1) antagonist SCH-23390, and no inhibition was produced by the D1 agonists fenoldopam or SKF-81247. When Na+ transport and Pf were stimulated with 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate plus 3-isobutyl-1-methylxanthine, dopamine did not inhibit, suggesting a "D2-type" receptor. However, the D2 agonist quinpirole had no effect on the AVP-dependent transepithelial voltage (VT), and the D2 and D3 antagonists domperidone and pimozide did not reverse dopamine inhibition of VT. The only agent tested that reversed the effects of dopamine was the D4-specific antagonist clozapine. We conclude that dopamine inhibition of salt and water transport in the CCD is mediated by a D4-like receptor.

Inhibition by epinephrine of AVP- and cAMP-stimulated Na+ and water transport in Dahl rat CCD

1993 ◽  
Vol 265 (3) ◽  
pp. F449-F460 ◽  
Author(s):  
C. T. Hawk ◽  
L. H. Kudo ◽  
A. J. Rouch ◽  
J. A. Schafer
Keyword(s):  
Water Transport ◽  
Bathing Solution ◽  
Sprague Dawley ◽  
Na Transport ◽  
Luminal Membrane ◽  
Osmotic Water ◽  
Depot Injection ◽  
Messenger System ◽  
Transepithelial Voltage ◽  
Dependent Transport

We examined the effects of epinephrine in perfused cortical collecting ducts (CCD) isolated from inbred Dahl-Rapp salt-sensitive (SS) and salt-resistant (SR) rats and from Sprague-Dawley (SD) rats. Rats were treated with 2.5 mg deoxycorticosterone pivalate (DOC; depot injection 4-9 days before study), and the CCD were treated with 220 pM vasopressin (AVP) to maximize Na+ transport. In CCD from all three strains 10 microM epinephrine in the bathing solution completely inhibited net Na+ transport, osmotic water permeability (Pf), and transepithelial voltage. In the SS CCD, epinephrine increased the fractional resistance of the luminal membrane to the same extent as 10 microM amiloride, indicating that it blocked the amiloride-sensitive conductance of the luminal membrane. Even at 100 nM epinephrine inhibited 80-100% of Na+ and water transport, and 1 microM yohimbine reversed or prevented these effects. In SS CCD, 0.1 mM 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) plus 0.1 mM 3-isobutyl-1-methylxanthine in place of AVP increased lumen-to-bath Na+ flux (J1-->b) from 56 +/- 5 to 143 +/- 3 pmol.min-1 x mm-1 and Pf from 6 +/- 12 to 1067 +/- 152 microns/s, but 100 mM epinephrine still significantly inhibited cAMP-stimulated J1-->b and Pf by 40 +/- 5% and 31 +/- 9%, respectively. Similar results were observed in the SR and SD rat CCD; however, the ability of yohimbine to reverse the epinephrine effect on cAMP-dependent transport was variable among the rat strains. We conclude that epinephrine acts via an alpha 2-receptor to inhibit adenylate cyclase but that at least one additional intracellular second messenger system may be involved.

Water permeability and pathways in the proximal tubule

1983 ◽  
Vol 245 (3) ◽  
pp. F279-F294 ◽  
Author(s):  
C. A. Berry
Keyword(s):  
Proximal Tubule ◽  
Water Transport ◽  
Water Permeability ◽  
Intercellular Space ◽  
Proximal Convoluted Tubule ◽  
Pressure Gradients ◽  
Solvent Drag ◽  
Lateral Intercellular Space ◽  
Volume Absorption ◽  
Osmotic Water

The route of water transport in the proximal tubule could be either transjunctional or transcellular. A transjunctional route is supported by data showing high osmotic-to-diffusive water permeability ratios, the possible correlation of junctional leakiness to ions and nonelectrolytes with water permeability, and solvent drag of nonelectrolytes and ions. These data, however, are not convincing. A transcellular route of water transport is supported by data showing that the osmotic water permeability (Pf) for apical and/or basolateral cell membranes is sufficiently high to account for the transepithelial Pf, making a tentative conclusion for a transcellular route of water transport possible. In addition, measurements of Pf have yielded insights into the mechanism of solute-solvent coupling. Pf has been reported to be mostly between 0.1 and 0.3 cm/s. In the rabbit proximal straight and the Necturus proximal convoluted tubule, in which water transport rates are low, this range of Pf will account for volume absorption with only small osmotic gradients (less than 6 mosmol). Higher osmotic gradients are required in the rat and possibly the rabbit proximal convoluted tubule, where water transport rates are higher. Solute-solvent coupling in all species is probably due to both luminal hypotonicity and lateral intercellular space hypertonicity. These two processes are directly linked. Mass balance requires that generation of luminal hypotonicity also generates a hypertonic absorbate and, thus, some degree of lateral intercellular space hypertonicity. It is likely that, in the rabbit at least, effective osmotic pressure gradients due to differences in solute reflection coefficients play little role in solute-solvent coupling.

Developmental changes in rabbit juxtamedullary proximal convoluted tubule water permeability

1996 ◽  
Vol 271 (4) ◽  
pp. F871-F876 ◽  
Author(s):  
R. Quigley ◽  
M. Baum
Keyword(s):  
Proximal Tubule ◽  
Water Transport ◽  
Water Permeability ◽  
Water Movement ◽  
Adult Rabbit ◽  
Osmotic Water ◽  
Glomerular Filtrate ◽  
Convoluted Tubules ◽  
Insight Into

The mammalian proximal tubule reabsorbs the bulk of the glomerular filtrate in a nearly isosmotic fashion due to the high osmotic water permeability (Pf) of this segment. Although the characteristics of proximal tubule water transport have been studied in the adult proximal tubule, little is known about the neonatal segment. The present study directly measured the Pf and diffusional water permeability (PDW) of neonatal (10 +/- 2 day old) and adult rabbit juxtamedullary proximal convoluted tubules (PCT) using in vitro microperfusion. The Pf of neonatal juxtamedullary PCT was greater than the Pf of adult juxtamedullary PCT. In contrast, the PDW was not different between the two groups. The Pf and PDW values of both neonatal and adult tubules were inhibited to the same degree by p-chloromercuribenzene sulfonate and had identical activation energies. The transepithelial reflection coefficients of NaCl and NaHCO3 were also found to be similar in both the neonatal and adult proximal tubules. Thus neonatal and adult juxtamedullary PCT have many characteristics of water transport that are identical; however, neonatal Pf is three to five times that of the adult value. This difference in Pf with identical PDW values may give an insight into the transepithelial pathway for water movement in the neonatal tubule.

scholarly journals Role of multiple phosphorylation sites in the COOH-terminal tail of aquaporin-2 for water transport: evidence against channel gating

2009 ◽  
Vol 296 (3) ◽  
pp. F649-F657 ◽  
Author(s):  
Hanne B. Moeller ◽  
Nanna MacAulay ◽  
Mark A. Knepper ◽  
Robert A. Fenton
Keyword(s):  
Plasma Membrane ◽  
Water Transport ◽  
Water Permeability ◽  
Laser Scanning Microscopy ◽  
Apical Plasma Membrane ◽  
Phosphorylation Sites ◽  
Osmotic Water Permeability ◽  
Aquaporin 2 ◽  
Osmotic Water

Arginine vasopressin (AVP)-regulated phosphorylation of the water channel aquaporin-2 (AQP2) at serine 256 (S256) is essential for its accumulation in the apical plasma membrane of collecting duct principal cells. In this study, we examined the role of additional AVP-regulated phosphorylation sites in the COOH-terminal tail of AQP2 on protein function. When expressed in Xenopus laevis oocytes, prevention of AQP2 phosphorylation at S256A (S256A-AQP2) reduced osmotic water permeability threefold compared with wild-type (WT) AQP2-injected oocytes. In contrast, prevention of AQP2 single phosphorylation at S261 (S261A), S264 (S264A), and S269 (S269A), or all three sites in combination had no significant effect on water permeability. Similarly, oocytes expressing S264D-AQP2 and S269D-AQP2, mimicking AQP2 phosphorylated at these residues, had similar water permeabilities to WT-AQP2-expressing oocytes. The use of high-resolution confocal laser-scanning microscopy, as well as biochemical analysis demonstrated that all AQP2 mutants, with the exception of S256A-AQP2, had equal abundance in the oocyte plasma membrane. Correlation of osmotic water permeability relative to plasma membrane abundance demonstrated that lack of phosphorylation at S256, S261, S264, or S269 had no effect on AQP2 unit water transport. Similarly, no effect on AQP2 unit water transport was observed for the 264D and 269D forms, indicating that phosphorylation of the COOH-terminal tail of AQP2 is not involved in gating of the channel. The use of phosphospecific antibodies demonstrated that AQP2 S256 phosphorylation is not dependent on any of the other phosphorylation sites, whereas S264 and S269 phosphorylation depend on prior phosphorylation of S256. In contrast, AQP2 S261 phosphorylation is independent of the phosphorylation status of S256.

Sevenfold-reduced osmotic water permeability in primary astrocyte cultures from AQP-4-deficient mice, measured by a fluorescence quenching method

2004 ◽  
Vol 286 (2) ◽  
pp. C426-C432 ◽  
Author(s):  
Eugen Solenov ◽  
Hiroyuki Watanabe ◽  
Geoffrey T. Manley ◽  
A. S. Verkman
Keyword(s):  
Fluorescence Quenching ◽  
Water Transport ◽  
Water Permeability ◽  
Cell Swelling ◽  
Osmotic Water Permeability ◽  
Wild Type ◽  
Osmotic Water ◽  
Fluorescence Quenching Method ◽  
Quenching Method ◽  
Deficient Mice

A calcein fluorescence quenching method was applied to measure osmotic water permeability in highly differentiated primary cultures of brain astrocytes from wild-type and aquaporin-4 (AQP-4)-deficient mice. Cells grown on coverglasses were loaded with calcein for measurement of volume changes after osmotic challenge. Hypotonic shock producing twofold cell swelling resulted in a reversible ∼12% increase in calcein fluorescence, which was independent of cytosolic calcein concentration at levels well below where calcein self-quenching occurs. Calcein fluorescence was quenched in <200 ms in response to addition of cytosol in vitro, indicating that the fluorescence signal arises from changes in cytosol concentration. In astrocytes from wild-type CD1 mice, calcein fluorescence increased reversibly in response to hypotonic challenge with a half-time of 0.92 ± 0.05 s at 23°C, corresponding to an osmotic water permeability ( Pf) of ∼0.05 cm/s. Pf was reduced 7.1-fold in astrocytes from AQP-4-deficient mice. Temperature dependence studies indicated an increased Arrhenius activation energy for water transport in AQP-4-deficient astrocytes (11.3 ± 0.5 vs. 5.5 ± 0.4 kcal/mol). Our studies establish a calcein quenching method for measurement of cell membrane water permeability and indicate that AQP-4 provides the principal route for water transport in astrocytes.

scholarly journals Colon water transport in transgenic mice lacking aquaporin-4 water channels

2000 ◽  
Vol 279 (2) ◽  
pp. G463-G470 ◽  
Author(s):  
Kasper S. Wang ◽  
Tonghui Ma ◽  
Ferda Filiz ◽  
A. S. Verkman ◽  
J. Augusto Bastidas
Keyword(s):  
Water Content ◽  
Water Transport ◽  
Water Permeability ◽  
Basolateral Membrane ◽  
Distal Colon ◽  
Water Channels ◽  
Proximal Colon ◽  
Aquaporin 4 ◽  
Osmotic Water Permeability ◽  
Osmotic Water

Transgenic null mice were used to test the hypothesis that water channel aquaporin-4 (AQP4) is involved in colon water transport and fecal dehydration. AQP4 was immunolocalized to the basolateral membrane of colonic surface epithelium of wild-type (+/+) mice and was absent in AQP4 null (−/−) mice. The transepithelial osmotic water permeability coefficient ( P f) of in vivo perfused colon of +/+ mice, measured using the volume marker 14C-labeled polyethylene glycol, was 0.016 ± 0.002 cm/s. P f of proximal colon was greater than that of distal colon (0.020 ± 0.004 vs. 0.009 ± 0.003 cm/s, P < 0.01). P f was significantly lower in −/− mice when measured in full-length colon (0.009 ± 0.002 cm/s, P< 0.05) and proximal colon (0.013 ± 0.002 cm/s, P< 0.05) but not in distal colon. There was no difference in water content of cecal stool from +/+ vs. −/− mice (0.80 ± 0.01 vs. 0.81 ± 0.01), but there was a slightly higher water content in defecated stool from −/− mice (0.68 ± 0.01 vs. 0.65 ± 0.01, P < 0.05). Despite the differences in water permeability with AQP4 deletion, theophylline-induced secretion was not impaired (50 ± 9 vs. 51 ± 8 μl · min−1 · g−1). These results provide evidence that transcellular water transport through AQP4 water channels in colonic epithelium facilitates transepithelial osmotic water permeability but has little or no effect on colonic fluid secretion or fecal dehydration.

scholarly journals Importance of the mercury-sensitive cysteine on function and routing of AQP1 and AQP2 in oocytes

1997 ◽  
Vol 273 (3) ◽  
pp. F451-F456 ◽  
Author(s):  
S. M. Mulders ◽  
J. P. Rijss ◽  
A. Hartog ◽  
R. J. Bindels ◽  
C. H. van Os ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Water Transport ◽  
Water Permeability ◽  
Nephrogenic Diabetes Insipidus ◽  
Osmotic Water Permeability ◽  
Wild Type ◽  
Mutant Proteins ◽  
Osmotic Water ◽  
Structural Differences

To discriminate between water transport of of aquaporin-2 (AQP2) mutants in nephrogenic diabetes insipidus and that of an AQP2 molecule used to drag them to the oolemma, we investigated the mercury sensitivity of wild-type and AQP2 C181S proteins in oocytes. Incubation with HgCl2 inhibited the osmotic water permeability (Pf) of human (h) AQP2 by 40%, whereas inhibition of hAQP1 was 75%. Oocytes expressing hAQP1 C189S revealed a Pf comparable to wild-type hAQP1, but mercury sensitivity was lost. In contrast, no increase in Pf was obtained when hAQP2 C181S was expressed. Also, expression of rat AQP2 C181A and C181S mutants did not increase the Pf, which contrasts with published observations. Immunocytochemistry and immunoblotting revealed that only AQP1, AQP1 C189S, and AQP2 were targeted to the plasma membrane and that AQP2 mutant proteins are retarded in the endoplasmic reticulum. In conclusion, water transport through AQP2 is less sensitive to mercury inhibition than through AQP1. Furthermore, substitution of the mercury-sensitive cysteine for a serine results in an impaired routing of human and rat AQP2. Similar mutations have no effect on AQP1 function, which is indicative of structural differences between AQP1 and AQP2.

scholarly journals Droplet-based microfluidic platform for measurement of rapid erythrocyte water transport

Lab on a Chip ◽  
2015 ◽  
Vol 15 (16) ◽  
pp. 3380-3390 ◽  
Author(s):  
Byung-Ju Jin ◽  
Cristina Esteva-Font ◽  
A. S. Verkman
Keyword(s):  
Water Transport ◽  
Water Permeability ◽  
Droplet Microfluidics ◽  
Osmotic Water Permeability ◽  
Fluorescence Image ◽  
Microfluidic Platform ◽  
Single Time ◽  
Osmotic Water

Osmotic water permeability was measured from a single, time-integrated fluorescence image using droplet microfluidics.

scholarly journals Light inactivation of water transport and protein–protein interactions of aquaporin–Killer Red chimeras

2011 ◽  
Vol 139 (1) ◽  
pp. 83-91 ◽  
Author(s):  
Florian Baumgart ◽  
Andrea Rossi ◽  
A.S. Verkman
Keyword(s):  
Water Transport ◽  
Protein Interactions ◽  
Water Permeability ◽  
Fluorescent Protein ◽  
Epifluorescence Microscopy ◽  
Live Cells ◽  
Wide Field ◽  
Protein Protein Interactions ◽  
Cell Plasma ◽  
Osmotic Water

Aquaporins (AQPs) have a broad range of cellular and organ functions; however, nontoxic inhibitors of AQP water transport are not available. Here, we applied chromophore-assisted light inactivation (CALI) to inhibit the water permeability of AQP1, and of two AQP4 isoforms (M1 and M23), one of which (M23) forms aggregates at the cell plasma membrane. Chimeras containing Killer Red (KR) and AQPs were generated with linkers of different lengths. Osmotic water permeability of cells expressing KR/AQP chimeras was measured from osmotic swelling–induced dilution of cytoplasmic chloride, which was detected using a genetically encoded chloride-sensing fluorescent protein. KR-AQP1 red fluorescence was bleached rapidly (∼10% per second) by wide-field epifluorescence microscopy. After KR bleaching, KR-AQP1 water permeability was reduced by up to 80% for the chimera with the shortest linker. Remarkably, CALI-induced reduction in AQP4-KR water permeability was approximately twice as efficient for the aggregate-forming M23 isoform; this suggests intermolecular CALI, which was confirmed by native gel electrophoresis on cells coexpressing M23-AQP4-KR and myc-tagged M23-AQP4. CALI also disrupted the interaction of AQP4 with a neuromyelitis optica autoantibody directed against an extracellular epitope on AQP4. CALI thus permits rapid, spatially targeted and irreversible reduction in AQP water permeability and interactions in live cells. Our data also support the utility of CALI to study protein–protein interactions as well as other membrane transporters and receptors.

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